课时6：PrepareStatement语句

1.PreparedStatement为预定义语句，继承Statement。
2.Statement只能静态操作SQL语句，如果要想动态操作SQL语句又该如何实现呢？例如：注册会员，这里可以使用PreparedStatement来动态操作SQL语句，PreparedStatement通过使用占位符“？”，来预生成SQL语句，从而达到动态操作的功能
3.实例
3.1

面向对象，就是尽量把对象定义成一个java文件，所有属性和操作都定义到里面。在其他函数中直接创建对象和调用对象



package com.geek99.demo;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class Test4 {

public static void main(String[] args) {
// insert("tom1","tom1@111111.com");
// Customer c = new Customer();
// c.setName("rose");
// c.setEmail("rose@1111.com");
// insert(c);

// c.setId(1);
// c.setName("dsfasdfa");
// update(c);

// del(2);
Customer c=query(3);
if(c!=null)
System.out.println(c.getName()+":"+c.getEmail());
}

static void insert(String name, String email) {
Connection conn = DBUtil.open();
String sql = "insert into CustomerTbl(name,email)values(?,?)";

try {
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, name);
pstmt.setString(2, email);
pstmt.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

static void insert(Customer c) {
Connection conn = DBUtil.open();
String sql = "insert into CustomerTbl(name,email)values(?,?)";

try {
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, c.getName());
pstmt.setString(2, c.getEmail());
pstmt.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

static void update(Customer c) {
Connection conn = DBUtil.open();
String sql = "update CustomerTbl set name=? where id=?";

try {
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, c.getName());
pstmt.setInt(2, c.getId());
pstmt.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

static void del(int id) {
Connection conn = DBUtil.open();
String sql = "delete from CustomerTbl where id=?";

try {
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, id);
pstmt.executeUpdate();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

static Customer query(int id) {
Connection conn = DBUtil.open();
String sql = "select id,name,email from CustomerTbl where id=?";

try {
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, id);
ResultSet rs=pstmt.executeQuery();
// pstmt.executeUpdate();

if(rs.next()){
String name=rs.getString(2);
String email=rs.getString(3);
Customer c=new Customer();
c.setId(id);
c.setName(name);
c.setEmail(email);
return c;
}

} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

}